In a conventional head-up display device which is mounted in an instrument panel of a vehicle, as disclosed in Patent Literature 1 for example, a window part of a chassis to which display light is to be emitted is covered with a light transmissive cover, and is constructed so as not to allow for entry of dust. In addition, the light transmissive cover that covers the window part is constructed to be curved in a longitudinal direction of a vehicle at an angle of inclination at which incident sunlight is reflected on a wall part of the instrument panel of the vehicle, so as not to dazzle persons inside and outside of the vehicle by the reflection of sunlight.